Alzheimer's disease (AD) is a presently incurable neurodegenerative disease affecting at least 12 million people worldwide. AD is predominantly a disease of the elderly, with a rate of incidence of about 1% of those aged 65 and rising to an estimated 40% by age 85. As the population as a whole grows older, because of medical advances, increasing life expectancies, and aging of the baby boomer generation, the overall incidence of AD is expected to rise and present even more of a burden to heath care systems and to patients and their caregivers and family.
No effective treatment of AD exists today. Currently available treatments such as Aricept® (donepezil HCl; Pfizer Corp.), Exelon® (rivastigmine tartrate; Novartis Pharmaceuticals Corp.) and Cognex® (tacrine; Warner Lambert Corp.) are intended to provide a measure of symptomatic relief for patients with mild to moderate AD and do not address the causes of the disease.
Clinical diagnosis of AD is also imperfect; accuracy varies from roughly 50-60% for general practitioners to 80-90% for Alzheimer's disease specialists at referral centers (Molsa et al., J. Neurol. Neurosurg. Psychiatry, 48 (11):1085-90 (1985); Rocca et al., Ann. Neurol., 19:415-424 (1986); Burns et al., BMJ, 301(6759):1026 (1990); Risse et al., Am. J. Psychiatry, 147(2):168-72 (1990); Gilleard et al., Acta Psychiatr. Scand., 85(4):264-9 (1992); Mendez et al., Alzheimer Dis. Assoc. Disord., 6:35-43 (1992); Fleming et al., Mayo Clin. Proc., 7:1093-1107 (1995); Corey-Bloom et al., Neurology, 45:211-218 (1995); and Bowler et al., J. Neurol. Neurosurg. Psychiatry, 64(1):18-24 (1998). There is an average delay of nearly three years from initial symptoms to when the diagnosis of AD is made (Jorst et al., J. Am. Geriatr. Soc., 43(11):1248-55 (1995)).
It has been recognized that a reliable biomarker would be of significant help in the accurate and early diagnosis of AD (Growdon et al., Neurobiol. Aging, 19:109-116 (1998)). Although several biochemical and genetic markers are currently available, their clinico-pathologic correlations are generally considered too low for routine clinical use. For example, apolipoprotein E ε4 allele is a genetic risk factor which is found only in 50% of AD cases (Myers et al., Neurology, 46(3):673-7 (1996)), and tau and β-amyloid protein measurements in cerebrospinal fluid (CSF) and serum Aβ have significant overlap between AD and non-AD levels, limiting their usefulness (Pirttila et al., J. Neurol. Sci., 127(1):90-5 (1994); Arai et al., Ann. Neurol., 38:649-652 (1995); Jensen et al., Neurosci. Lett., 186(2-3):189-91 (1995); Motter et al., Ann. Neurol., 38(4):643-8 (1995); Munroe et al., Ann. Clin. Lab. Sci., 25(3):207-17 (1995); Tata et al., J. Neurol. Neurosurg. Psychiatr., 59:280-283 (1995); Vigo-Pelfrey et al., Neurology, 45(4):788-93 (1995); Iwatsubo T., Neurobiol. Aging, 19:161-163 (1998); Nitsch et al., Ann. Neurol., 37(4):512-8 (1995); van Gool et al., Ann. Neurol., 37(2):277-9 (1995); Tamaoka et al., J. Neurol. Sci., 151(1-2):65-8 (1996); and Pirtilla et al., Arch. Neurol., 53(2):189-93 (1996)). Other proposed markers, such as pupillary response to tropicamide (Scinto et al., Science, 266:1051-1054 (1994); and Growdon et al., Arch. Neurol., 54(7):841-4 (1997)) and serum factors such as p-97 (Kennard et al., Nat. Med., 2(11):1230-5 (1996)), have not yet been validated in repeated controlled clinical studies. The major drawbacks of most proposed AD markers are that they are usually not brain-specific molecules associated with AD pathology and that they are not reliably measurable in peripheral fluids.
Neural thread proteins (NTP) are a novel family of recently characterized brain proteins. NTP is a ˜41 kD membrane associated phosphoprotein with functions related to neuritic sprouting and cell death (de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997); and de la Monte et al., Alz. Rep., 2:327-332 (1999)). There is compelling evidence linking NTP with AD. NTP mRNA is upregulated in AD brain compared to controls; NTP protein levels in brain and in CSF are higher in AD than controls; and NTP immunoreactivity is clearly found in senile plaques, in neurofibrillary tangles (NFT), in degenerating neurons, neuropil threads, and dystrophic neuritic sprouts in AD and Down syndrome brains (Ozturk et al., Proc. Natl. Acad. Sci. USA, 86:419-423 (1989); de la Monte et al., J. Clin. Invest., 86(3):1004-13 (1990); de la Monte et al., J. Neurol. Sci., 113(2):152-64 (1992); de la Monte et al., Ann. Neurol., 32(6):733-42 (1992); de la Monte et al., J. Neuropathol. Exp. Neurol., 55(10):1038-50 (1996), de la Monte et al., J. Neurol. Sci., 138(1-2):26-35 (1996); de la Monte et al., J. Neurol. Sci., 135(2):118-25 (1996); de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997); and de la Monte et al., Alz. Rep., 2:327-332 (1999)). NTP accumulation in neurons occurs early in AD neurodegeneration (before NFT formation). NTP has also been identified Down's Syndrome brain tissue (Wands et al., International Patent Publication No. WO 90/06993; de la Monte et al., Alz. Rep., 2:327-332 (1999)). Most patients with Down's Syndrome exhibit neuropathology similar to that of AD after middle age and develop many cognitive defects similar to those of AD later in life.
NTP levels in the cerebrospinal fluid (CSF) of AD patients and controls were shown to be consistently elevated in AD (Chong et al., J. Clin. Lab. Anal., 6(6):379-83 (1992); de la Monte et al., Ann. Neurol., 32:733-742 (1992); de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997); Ghanbari et al., J. Clin. Lab. Anal., 12(4):223-6 (1998); Ghanbari et al., J. Contemp. Neurol., 1998:2-8 (1998); Kahle et al., Neurology, 54(7):1498-504 (2000)). Specificity of NTP elevation in AD was shown in comparison to non-AD neurological disease controls, and NTP elevation was positively correlated with degree of dementia (de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997); and de la Monte et al., Alz. Rep., 2:327-332 (1999); and Kahle et al., Neurology, 54(7):1498-504 (2000)). In one major study, 89% of patients with early AD had NTP levels of above 2 ng/mL of CSF and 89% of non-AD controls below 2 ng/mL of CSF (de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997)).
Subsequently, the NTP protein was identified in urine by high performance liquid chromatography, capillary electrophoresis, and ELISA (Ghanbari et al., J. Clin. Lab. Anal., 12(4):285-288 (1998); and de la Monte et al., Alz. Rep., 2:327-332 (1999)). Urinary NTP levels were found to correlate with CSF levels in AD patients and controls and to be significantly elevated in AD patients as compared to non-AD patients (Ghanbari et al., J. Clin. Lab. Anal., 12(4):285-288 (1998)). An assay using gold particles with bound monoclonal anti-NTP in the liquid phase was developed for urine samples and demonstrated to be both highly sensitive and specific for AD (Fitzpatrick et al., Alzheimer's Reports, 3(3):155-159 (2000)).
There is a need to improve upon the existing assays for NTP, including a need to develop point-of-care assays for NTP which can be conducted in a general medical laboratory or a doctor's office. Technical advances such as methods to routinely purify native NTP from urine in a cost-effective manner or the development of easily manufactured analogs to NTP would also improve any such assays
There is evidence showing that NTP may play a direct role in the pathogenesis of AD, thereby making it a target for drug development for the treatment of AD. NTP is associated with neuritic sprouting; abnormal neuritic sprouting is associated with AD. Over-expression of NTP can cause cellular accumulations of phospho-tau, which in turn precedes the formation of NFT, an important neuroanatomical correlate of dementia in AD (de la Monte et al., Alz. Rep., 2:327-332 (1999)). In addition, over-expression of NTP can cause increased cell death of an apoptotic nature linked to oxidative stress (de la Monte et al., 1999). Inhibiting the expression or the biochemical action of NTP offers one promising route to an effective treatment for AD.
The gene and predicted protein sequence for NTP has been identified and described (de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997)). Neural thread protein was first described and claimed in U.S. Pat. Nos. 5,948,634; 5,948,888; and 5,830,670, all for “Neural Thread Protein Gene Expression and Detection of Alzheimer's Disease.”
Other species of neural thread protein (˜26 kD, ˜21 kD, ˜17 kD and ˜15 kD) have been identified and associated with neuroectodermal tumors, astrocytomas, and glioblastomas and with injury due to hypoxia, ischemia, or cerebral infarction (de la Monte et al., J. Neuropathol. Exp. Neurol., 55(10):1038-50 (1996), de la Monte et al., J. Neurol. Sci., 138(1-2):26-35 (1996); de la Monte et al., J. Neurol. Sci., 135(2):118-25 (1996); de la Monte et al., J. Clin. Invest., 100:3093-3104 (1997); and de la Monte et al., Alz. Rep., 2:327-332 (1999)).
There is a need in the art for improved NTP compositions, useful in therapeutics and diagnostics related to AD and Down's Syndrome, and for compositions relating to the other species of neural thread protein useful in threapeutics and diagnostics for neuroectodermal tumors, astrocytomas, glioblastomas, and other neurodegenerative disorders and for injury due to hypoxia, ischemia and cerebral infarction. The present invention satisfies these needs.